Photographic silver-halid emulsion



Patented July 2, 1929.

OTTO MATTHIES AND WALTER DIETERLE,

PATENT OFFICE.

or DESSAU, Ann JOSEF nnrrs'rorrnn, or

BERLIN-FRIEDENAU, GERMANY, ASSIGNORS, BY MESNE ASSIGNMENTS, T AGFA. ANSCO CORPORATION, OF BINGHAMTON, NEW YORK, A CORPORATION 01 NE Yonx.

No Drawing. Application filed August 8, 1926, Serial No. 127,708, and in Germany September 14, 1925.

The sensitivity reached in maturing silver halid emulsions depends highly on the gela kaline fermentative hydrolysis and a simultaneous artial oxidation. These products of hydro ysis, after having been neutralized,

can be addeddi'rectly in the diluted form as they are obtained, or the effective compounds contained therein may first be enriched or 0 isolated. Thefproducts of decomposition may be prepared, e. g. from albumin, keratin, gelatine, -cystine., animal hide, tendons, cartilages, horn, bone or other raw materials for glue and gelatine.

It has already been proposed to increase the sensitivity of silver halid emulsions by adding during emulsion making, products resulting from a treatment of proteins,.but it has been supposed up to now that decomposit1on in this process would be detrimental to the ability to increase sensitivity and it has always been prescribed to thoroughly avoid any oxidation or bacterial action, i. e., fermentative influence. Thus proteins heretofore have been acted upon for the purpose of producing sensitivity increasing products only in a very mild, way. Thus it has been suggested to extract gelatine with distilled water at 30 C. or to extract deliming solu- 40 tions or powdered pods with organic solvents.

lVe have found that by the decomposition of proteins highly valuable products for the purpose set forth can be obtained. The decomposition may be carried on by hydrolysis,

e. g., alkaline hydrolysis, and by initiating oxidation. Such a treatment has been thought to be highly harmful in prior art. It is obvious that the products obtained according to our present invention differ greatly from any prior roducts intended for the same purpose,

since t 1ey are breakdown roducts while heretofore only extracts have een thought applicable. Furthermore, the products extracted by organic solvents are distinguished from our breakdown products by their solubility. Our breakdown products are soluble only in Water. I

Since all roteins from animal as well as from vegeta 1e sources may be regarded as aggregates combined of a few fundamental units in varying amounts and in various configurations. the decomposition of any protcins according to the present invention finally yields a solution of nearly the same products, the amount of which only varies with the different sources of material.

In preparing these products the point at which the decomposition by hydrolysis and partial oxidation is to be stopped, is determined by the refractive index curve of the solution and by testing at regular intervals the photographic qualities of the decomposition products. During the decomposing of proteins the solution shows a continuous increase in the refractive index which tends to reach a constant value when all protein present has been broken down. The photographic test is carried out by making a small batch of emulsion with addition of varying amounts of the product to be tested. From the sensitogram of the resulting emulsion the photographic qualities of the product are eas ly judged. The decomposing treatment 1s 1nterrupted when a photographic optlmum 1s reached. In the same way the quantitynecessary for any emulsion may be determined.

By the addition of these products durmg emulsion making, to the constituents ofthe emulsion or only to the finished emulsion, one succeeds in obtaining high speed emulsions though employing a photographically unsensitve gelatine.

Examples.

gelatine or 100 g. of calf stock in alkaline solution and adding the neutralized solution during emulsion making or to the gelatine as described in Example 1. i

3. 100 g. gelatine are hydrolized ati37 C.

' during some hours by panereatin While keeping the pH-value of the solution at 8 approximately, and the resulting solution is added during emulsion making or to one of the constituents of the emulsion as described in Ex' ample 1. 1

Having now particularly described and ascertained the nature of our said invention and in what manner it is to be performed we declare that what We claim is:

1. In the manufacture of photographic silver halid emulsions, the addition to the emulsion of a sensitivity increasing material prepared by alkaline hydrolysis and simultaneous partial oxidation of proteins.

2. In the manufacture of photographic silver halid emulsions, theaddition to the constituents of the emulsionof a sensitivity increasing material prepared by alkaline hydrolysis and simultaneous partial oxidation of proteins.

3. In the manufacture of photographic silver halid emulsions, the addition to the emulsion of a sensitivity increasing material prepared by alkaline fermentative. hydrolysis and simultaneous partial oxidation of proteins.

4. In the manufacture of photographic silver halid emulsions, the addition to the constituents of the emulsion of a sensitivity increasing material prepared by alkaline fermcntative hydrolysis and simultaneous partial oxidation of proteins. 5. Silver halld emulsions having added 

